I am having the same problems with Widget Renderer TreeGrid. Like in example (you can see the attachement) I created custom renderer for my grid. But after some operations (i.e. open all leaves and start collapsing-expanding them) some widgets get lost and not displayed.

The problem seems to be that in IE when you scroll/filter it makes getWidget()... For some reason the widget already build gets a bad html. So, for the moment the problem is solved by rebuilding the widget everytime (checkbox in my case) with listeners and everything. It's not so good for performance but it seems more stable. Will see what the tests in time will give.